与此处的其他几篇文章一样,我正在尝试创建一个ListView,其中包含每行的CheckBox,并使用sqlite数据库存储选择的当前状态.
从http://appfulcrum.com/?p=351的示例开始,这个示例并不完全正常,我创建了一个创建数据库的简单应用程序,用20个项目填充它,并显示列表.
它成功检索状态并存储选择的状态.
但是,如果我更改它,它无法正确显示CheckBox状态,滚动到列表的另一端,然后向后滚动.例如如果我选择第一个CheckBox,滚动到底部,然后回到顶部,不再设置CheckBox.这是在Android 2.1三星手机上运行.
如果我返回主屏幕,返回列表,CheckBox已正确设置,因此数据库确实已更新.
该示例扩展了SimpleCursorAdapter,并且getView()根据表中选择列的值,根据需要使用true或false调用setChecked().
以下是所有来源.
我当然很感激被告知,“呃,这是你的问题……”
CustomListViewDB.java
// src/CustomListViewDB.java
package com.appfulcrum.blog.examples.listviewcustomdb;
import android.app.ListActivity;
import android.database.Cursor;
import android.database.sqlException;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;
public class CustomListViewDB extends ListActivity {
private ListView mainListView = null;
CustomsqlCursorAdapter adapter = null;
private sqlHelper dbHelper = null;
private Cursor currentCursor = null;
private ListView listView = null;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.simple);
if (this.dbHelper == null) {
this.dbHelper = new sqlHelper(this);
}
listView = getListView();
listView.setItemsCanFocus(false);
listView.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
//listView.setClickable(true);
Button btnClear = (Button) findViewById(R.id.btnClear);
btnClear.setonClickListener(new OnClickListener() {
public void onClick(View v) {
Toast.makeText(getApplicationContext()," You clicked Clear button",Toast.LENGTH_SHORT).show();
ClearDBSelections();
}
});
new SelectDataTask().execute();
this.mainListView = getListView();
mainListView.setCacheColorHint(0);
}
@Override
protected void onRestart() {
super.onRestart();
new SelectDataTask().execute();
}
@Override
protected void onPause() {
super.onPause();
this.dbHelper.close();
}
protected void ClearDBSelections() {
this.adapter.ClearSelections();
}
private class SelectDataTask extends AsyncTask<Void,Void,String> {
protected String doInBackground(Void... params) {
try {
CustomListViewDB.this.dbHelper.createDatabase(dbHelper.dbsqlite);
CustomListViewDB.this.dbHelper.openDataBase();
CustomListViewDB.this.currentCursor = CustomListViewDB.this.dbHelper
.getCursor();
} catch (sqlException sqle) {
throw sqle;
}
return null;
}
// can use UI thread here
protected void onPostExecute(final String result) {
startManagingCursor(CustomListViewDB.this.currentCursor);
int[] listFields = new int[] { R.id.txtTitle };
String[] dbColumns = new String[] { sqlHelper.COLUMN_TITLE };
CustomListViewDB.this.adapter = new CustomsqlCursorAdapter(
CustomListViewDB.this,R.layout.single_item,CustomListViewDB.this.currentCursor,dbColumns,listFields,CustomListViewDB.this.dbHelper);
setlistadapter(CustomListViewDB.this.adapter);
}
}
}
CustomsqlCursorAdapter.java
// src/CustomsqlCursorAdapter.java
package com.appfulcrum.blog.examples.listviewcustomdb;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlException;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedchangelistener;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;
public class CustomsqlCursorAdapter extends SimpleCursorAdapter {
private Context mContext;
private sqlHelper mDbHelper;
private Cursor mCurrentCursor;
public CustomsqlCursorAdapter(Context context,int layout,Cursor c,String[] from,int[] to,sqlHelper dbHelper) {
super(context,layout,c,from,to);
this.mCurrentCursor = c;
this.mContext = context;
this.mDbHelper = dbHelper;
}
public View getView(int pos,View inView,ViewGroup parent) {
View v = inView;
if (v == null) {
LayoutInflater inflater = (LayoutInflater) mContext
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = inflater.inflate(R.layout.single_item,null);
}
if (!this.mCurrentCursor.movetoPosition(pos)) {
throw new sqlException("CustomsqlCursorAdapter.getView: Unable to move to position: "+pos);
}
CheckBox cBox = (CheckBox) v.findViewById(R.id.bcheck);
// save the row's _id value in the checkBox's tag for retrieval later
cBox.setTag(Integer.valueOf(this.mCurrentCursor.getInt(0)));
if (this.mCurrentCursor.getInt(sqlHelper.COLUMN_SELECTED_idx) != 0) {
cBox.setChecked(true);
Log.w("sqlHelper","CheckBox true for pos "+pos+",id="+this.mCurrentCursor.getInt(0));
} else {
cBox.setChecked(false);
Log.w("sqlHelper","CheckBox false for pos "+pos+",id="+this.mCurrentCursor.getInt(0));
}
//cBox.setonClickListener(this);
cBox.setonCheckedchangelistener(new OnCheckedchangelistener() {
@Override
public void onCheckedChanged(CompoundButton buttonView,boolean isChecked) {
Log.w("sqlHelper","Selected a CheckBox and in onCheckedChanged: "+isChecked);
Integer _id = (Integer) buttonView.getTag();
ContentValues values = new ContentValues();
values.put(sqlHelper.COLUMN_SELECTED,isChecked ? Integer.valueOf(1) : Integer.valueOf(0));
mDbHelper.dbsqlite.beginTransaction();
try {
if (mDbHelper.dbsqlite.update(sqlHelper.TABLE_NAME,values,"_id=?",new String[] { Integer.toString(_id) }) != 1) {
throw new sqlException("onCheckedChanged Failed to update _id="+_id);
}
mDbHelper.dbsqlite.setTransactionSuccessful();
} finally {
mDbHelper.dbsqlite.endTransaction();
}
Log.w("sqlHelper","-- _id="+_id+",isChecked="+isChecked);
}
});
TextView txtTitle = (TextView) v.findViewById(R.id.txtTitle);
txtTitle.setText(this.mCurrentCursor.getString(this.mCurrentCursor
.getColumnIndex(sqlHelper.COLUMN_TITLE)));
return (v);
}
public void ClearSelections() {
this.mDbHelper.clearSelections();
this.mCurrentCursor.requery();
}
}
ListViewWithDBActivity.java
package com.appfulcrum.blog.examples.listviewcustomdb;
import android.app.Activity;
import android.os.Bundle;
public class ListViewWithDBActivity extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}
提供sqlHelper
// sqlHelper.java
package com.appfulcrum.blog.examples.listviewcustomdb;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlException;
import android.database.sqlite.sqliteDatabase;
import android.database.sqlite.sqliteOpenHelper;
import android.database.sqlite.sqliteQueryBuilder;
import android.database.sqlite.sqliteStatement;
import android.util.Log;
public class sqlHelper extends sqliteOpenHelper {
private static final String DATABASE_PATH = "/data/data/com.appfulcrum.blog.examples.listviewcustomdb/databases/";
public static final String DATABASE_NAME = "TodoList";
public static final String TABLE_NAME = "TodoItems";
public static final int TodoItems_VERSION = 1;
public static final String COLUMN_ID = "_id"; // 0
public static final String COLUMN_TITLE = "title"; // 1
public static final String COLUMN_NAME_DESC = "description";// 2
public static final String COLUMN_SELECTED = "selected"; // 3
public static final int COLUMN_SELECTED_idx = 3;
public sqliteDatabase dbsqlite;
private Context mContext;
public sqlHelper(Context context) {
super(context,DATABASE_NAME,null,1);
mContext = context;
}
@Override
public void onCreate(sqliteDatabase db) {
createDB(db);
}
@Override
public void onUpgrade(sqliteDatabase db,int oldVersion,int newVersion) {
Log.w("sqlHelper","Upgrading database from version " + oldVersion
+ " to " + newVersion + ",which will destroy all old data");
db.execsql("DROP TABLE IF EXISTS TodoItems;");
createDB(db);
}
public void createDatabase(sqliteDatabase db) {
createDB(db);
}
private void createDB(sqliteDatabase db) {
if (db == null) {
db = mContext.openorCreateDatabase(DATABASE_NAME,null);
}
db.execsql("CREATE TABLE IF NOT EXISTS TodoItems (_id INTEGER PRIMARY KEY,title TEXT,"
+" description TEXT,selected INTEGER);");
db.setVersion(TodoItems_VERSION);
//
// Generate a few rows for an example
//
// find out how many rows already exist,and make sure there's some minimum
sqliteStatement s = db.compileStatement("select count(*) from TodoItems;");
long count = s.simpleQueryForLong();
for (int i = 0; i < 20-count; i++) {
db.execsql("INSERT INTO TodoItems VALUES(NULL,'Task #"+i+"','Description #"+i+"',0);");
}
}
public void openDataBase() throws sqlException {
String myPath = DATABASE_PATH + DATABASE_NAME;
dbsqlite = sqliteDatabase.openDatabase(myPath,sqliteDatabase.OPEN_READWRITE);
}
@Override
public synchronized void close() {
if (dbsqlite != null)
dbsqlite.close();
super.close();
}
public Cursor getCursor() {
sqliteQueryBuilder queryBuilder = new sqliteQueryBuilder();
queryBuilder.setTables(TABLE_NAME);
String[] asColumnsToReturn = new String[] { COLUMN_ID,COLUMN_TITLE,COLUMN_NAME_DESC,COLUMN_SELECTED };
Cursor mCursor = queryBuilder.query(dbsqlite,asColumnsToReturn,COLUMN_ID+" ASC");
return mCursor;
}
public void clearSelections() {
ContentValues values = new ContentValues();
values.put(COLUMN_SELECTED,0);
this.dbsqlite.update(sqlHelper.TABLE_NAME,null);
}
}
Start.java
//src/Start.java
package com.appfulcrum.blog.examples.listviewcustomdb;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;
public class Start extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button btnSimple = (Button) findViewById(R.id.btnSimple);
btnSimple.setonClickListener(new OnClickListener() {
public void onClick(View v) {
Toast.makeText(getApplicationContext()," You clicked ListView From DB button",Toast.LENGTH_SHORT).show();
Intent intent = new Intent(v.getContext(),CustomListViewDB.class);
startActivityForResult(intent,0);
}
});
}
}
布局/ main.xml中
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/buttonlayout" android:orientation="vertical"
android:layout_width="fill_parent" android:layout_height="fill_parent"
android:gravity="left|top" android:paddingTop="2dp"
android:paddingBottom="2dp">
<TextView android:id="@+id/txtTest" android:layout_width="fill_parent"
android:layout_height="wrap_content" android:textStyle="bold"
android:text="@string/app_name" android:textSize="15sp"
android:textColor="#FF0000" android:gravity="center_vertical"
android:paddingLeft="5dp">
</TextView>
<Button android:id="@+id/btnSimple"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="15sp"
android:text="Listview from DB"
android:textColor="#000000"
>
</Button>
</LinearLayout>
布局/ simple.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="fill_parent"
android:layout_height="fill_parent">
<LinearLayout android:id="@+id/buttonlayout"
android:orientation="horizontal" android:layout_width="fill_parent"
android:layout_height="wrap_content" android:height="32dp"
android:gravity="left|top" android:paddingTop="2dp"
android:paddingBottom="2dp">
<LinearLayout android:id="@+id/buttonlayout2"
android:orientation="horizontal" android:layout_height="wrap_content"
android:gravity="left|center_vertical" android:layout_width="wrap_content"
android:layout_gravity="left|center_vertical">
<TextView android:id="@+id/txtTest"
android:layout_width="fill_parent"
android:layout_height="fill_parent" android:textStyle="bold"
android:text="@string/list_header" android:textSize="15sp"
android:gravity="center_vertical" android:paddingLeft="5dp">
</TextView>
<Button android:id="@+id/btnClear"
android:layout_width="wrap_content"
android:layout_height="wrap_content" android:text="Clear"
android:textSize="15sp" android:layout_marginLeft="10px"
android:layout_marginRight="10px"
android:layout_marginBottom="2px"
android:layout_marginTop="2px" android:height="15dp"
android:width="70dp"></Button>
</LinearLayout>
</LinearLayout>
<TableLayout android:id="@+id/TableLayout01"
android:layout_width="fill_parent" android:layout_height="fill_parent"
android:stretchColumns="*">
<TableRow>
<ListView android:id="@android:id/list"
android:layout_width="wrap_content"
android:layout_height="wrap_content"></ListView>
</TableRow>
</TableLayout>
</LinearLayout>
布局/ single_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent" android:layout_height="wrap_content"
android:orientation="horizontal" android:gravity="center_vertical">
<CheckBox android:id="@+id/bcheck"
android:layout_width="wrap_content"
android:layout_height="fill_parent" />
<TextView android:id="@+id/txtTitle"
android:layout_width="wrap_content" android:gravity="left|center_vertical"
android:layout_height="?android:attr/listPreferredItemHeight"
android:layout_alignParentLeft="true"
android:textSize="20sp" android:text="Test"
android:textStyle="bold" android:paddingLeft="5dp"
android:paddingRight="2dp" android:focusable="false"
android:focusableInTouchMode="false"></TextView>
<LinearLayout android:layout_width="fill_parent"
android:layout_height="wrap_content" android:orientation="horizontal"
android:gravity="right|center_vertical">
</LinearLayout>
</LinearLayout>
值/ strings.xml中
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="hello">Hello World,ListViewWithDBActivity!</string>
<string name="app_name">ListViewWithDB</string>
<string name="list_header">List Headers</string>
</resources>
AndroidManifest.xml中
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
android:versionCode="1" android:versionName="1.0"
package="com.appfulcrum.blog.examples.listviewcustomdb">
<application android:icon="@drawable/icon"
android:label="@string/app_name"
android:theme="@android:style/Theme.NoTitleBar">
>
<activity android:name=".Start" android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".CustomListViewDB"></activity>
</application>
<uses-sdk android:minSdkVersion="7" /> <!-- android 1.6 -->
</manifest>
如果你想构建,将一些任意的icon.png扔进drawable.
提前致谢.
解决方法
我发现异地问题最完整的解决方案.
在Android ListView with CheckBox : Retain State
感谢帮助人员.